Molding methods, molds and products

ABSTRACT

A method of manufacturing plates assembleable in a stack to provide a mold to form fastener elements includes applying a photoresist material to at least one side of the plate. The photoresist material is exposed to light. Portions of the photoresist material are removed based on the light exposure. Acid is applied to the plate, dissolving portions of the plate exposed to the acid and creating cavities.

BACKGROUND OF THE INVENTION

This invention relates to molding methods and products and to the makingof molded hook fasteners for engaging low loft fabrics.

In the field of molded hook fasteners, typically a series of adjacentrows of hooks forms one side of a fastener and a mating member providesloops or anchored fibers with which the hooks engage.

A fastener element with rows of hook members is typically formed with amolding tool that has no moving parts. The hooks are pulled from theirmold cavities by distorting the hooks. For molding continuous strips ofsuch hook members, a rotating molding roll is employed while fordiscrete items, injection molding techniques are employed. Improvementsapplicable to such molds and to the processes of molding these hookmembers may be useful in molding other products.

SUMMARY OF THE INVENTION

It is realized that molded fastener hooks with very small hooks, i.e. ofheight less than 0.020 in., can provide better engagement with low-lyingloops or fibers of inexpensive fabrics because the probability isincreased that each hook of a fastener will engage a loop or fiber.

There are a number of seemingly conflicting considerations that stand inthe way of realizing this objective in a manner that provides highlyeffective fastening. As the hook members become smaller and thinner,they become more flexible. This increases the tendency for hooks underslight load to disengage from the mating fabric. It is usually importantthat such small hook members present a significant re-entrant crook,i.e. a hook tip that tilts downwardly, in order to better snag andretain the loops or fibers of the mating fabric. It also is importantthat the crook of the hook have a very low displacement volume to enablesufficient penetration into low loft fabrics to enable loop or fiberengagement. Crook displacement volumes, as defined below, of less than1.0×10⁻⁶ in.³ and preferably about 0.5×10⁻⁶ in.³ or less are desired. Itis of course also important that the peel and shear strengths of theoverall fastener meet the strength demands of the conditions of use.Consequently, the hooks and the loops must have sufficient strength tomaintain engagement but also sufficient flexibility to disengage withoutdestroying the hooks or the loops.

The preferred known technique for making high performance hooks has beento employ molds that have no moving parts, but hooks of the size ofinterest here are especially difficult to achieve by such conventionaltechniques.

The present invention provides improved molds and techniques for makingthe hooks and other products, improved techniques for making the molds,and improved products.

According to one aspect of the invention we have realized that effectivemolded hook members of height less than 0.020 in., that have efficientloop or fiber engaging crooks and displacement volumes of less than1.0×10⁻⁶ in .³ and preferably about 0.5×10⁻⁶ in.³ or less (such hooksare sometimes referred to herein as microhooks), can be reliablyproduced at high speed and low cost by use of special shape parametersfor the mold cavity in which the hook is formed.

A conventional mold cavity defines a hook profile consisting of arelatively short base or pedestal, a relatively elongated stem section,and a crook or return section. We have realized that an effectivemicrohook can instead be formed by use of a mold cavity profile that isdefined essentially by a pedestal portion to which a tapered crookportion is directly joined.

In a preferred microhook mold cavity, the base width and taper rate arealso important. Preferably, the base is at least about 100% of theoverall hook height, more preferably at least about 110% or more.Preferably, the taper (rate of change of width relative to distancealong the hook axis) of the hook cavity from its base at least to alevel of half of the height of the hook cavity is greater than 0.6 to 1,more preferably greater than 0.8 to 1 and most preferably greater than1.0 to 1.0.

In preferred profiles of this kind, the pedestal cavity has a muchlarger taper from its base to the midsection of the hook than the taperof the crook section. A pedestal taper of more than four times andpreferably more than five times the taper of the crook portion isemployed. In preferred implementations, the sides of the profile of themold cavity are straight and a projection of the converging sidesintersect at an apex angle of 40° or more, preferably, at least 50° andin the presently preferred implementation, 60°.

Such mold constructions produce hooks that are strong for their size andenable a high density of the hooks to be achieved.

Such mold constructions also enable the molded crook portion of thehook, after undergoing deformation during withdrawal from the fixed moldcavity, to be rapidly exposed to an expansion space that quickly givesroom for the crook portion to recover toward its originally molded form.

By use of these novel mold cavity parameters, we realize that certainconditions in the molding of microhooks can be overcome. Immediatelyupon molding in a cooled mold, a hook has a memory for its initialmolded condition. After being deformed the crook tends to return to theinitial form. However, if a hook member has a significant crook, itcannot be withdrawn from a fixed mold unless it remains warm and readilydeformable. To the extent the hook member cools while being withdrawn, atendency is introduced for the hook to set in the deformed condition,and not return sufficiently to the designed crook shape.

These factors have been present in the molding of hook members of largerform, but have not appeared critical.

We realize, however, that with microhooks, these factors can be morecritical: because the very small crook tips have a significantlyincreased ratio of exposed cooling surface relative to mass, thefabric-engaging crooks tend to cool and set more quickly than do moldedhook elements of the conventional larger form. With the novel moldcavity parameters provided by the present invention, the degree ofsetting in deformed state can be decreased because the relative durationof exposure of the hook member to the deformed condition is decreased.This enables effective production of microhooks having a high level ofperformance.

We have realized that products made with the mold profile and techniquesjust described have other advantages, even where rapid recovery of thehook tip shape is not important. The wide based pedestal to which thecrook is directly attached provides a profile with considerable strengthin shear loading. Accordingly, the cross-row thickness of the hook canbe less than the conventional thickness of 0.008 in. or more; preferablythe hook has a thickness of 0.006 in. or less. Likewise the spacingbetween adjacent rows of hooks can be less than about 0.010 in.,preferably about 0.008 in. or less. Density of distribution of the hooksin the direction cross-wise to the direction of the rows of hooks ofabout 50 per in. or more can be advantageously achieved, preferablyabout 70 hooks per in. or more.

The smallness of the hooks also enables densities of distribution in thedirection of the rows of hooks of about 20 hooks per in. or more,preferably about 25 hooks or more per in.

In particular it becomes possible to mold highly effective hook membersthat have an areal density greater than 1000 hooks per in. ², andpreferably greater than 1500 hooks per in.². Hook members of such arealdensity and form have been found to have an aggregate strength effectthat can meet the strength demands of many conditions of use, whileproviding a hook surface that is soft to the touch due to the aggregatesurface effect provided by the closely adjacent hooks. The preferreddownward orientation of the tips add to this effect. Each of thesefeatures makes the hook member useful on items that lie close to theskin.

When the molds are provided on a rotating molding roll, the mold profileof the invention enables particularly efficient production of runninglengths of many closely spaced rows of high performance hook member. Theinvention is also useful for fixed molds for use in injection molding.

Microhooks molds can advantageously be formed by use of EDM techniques.Though etching was previously tried and discarded in this field, it isseen that photochemical milling techniques have unique advantages to theformation of molds for microhooks. They enable the production of hooksthat are extremely small (less than 0.010 in. in height), so small thatwe term them "sub-microhooks". Furthermore, these techniques providevery smooth surfaces for the mold cavities. These have specialusefulness to produce hooks for use with extremely low loft materials.In certain circumstances laser machining and laser milling and use ofplating techniques also have advantage in the forming of the molds forthe unique products of the invention.

The invention also provides techniques for molding hook members that areoriented at various angles to the machine direction of a molding rolleror of molds formed by face-to-face assembly of the molding plates. Forthis purpose apertures in a number of thin plates cooperate to definethe mold cavity.

According to one aspect of the invention, a mold for integrally forminghook-shaped members on a sheet-form base from a moldable resin isprovided. The mold has hook-shaped cavities located at the surface ofthe mold. At least many of the hook-shaped cavities have a height of0.020 in. or less and a tapered pedestal chamber and a crook chamberwhich are contiguous.

According to another aspect of this invention a mold for integrallyforming hook-shaped members on a sheet-form base from a moldable resinis provided. The mold has hook-shaped cavities located at the surface ofthe mold. At least many of the hook-shaped cavities have a height of0.020 in. or less and a tapered pedestal chamber and a crook chamberwhich are contiguous. The pedestal chamber has a base width greater thanabout the height of the hook-shaped cavity. At half height of thehook-shaped cavity, the pedestal chamber also has a width equal to abouthalf the height of the hook-shaped cavity or more.

According to another aspect of the invention, a roll having molds forintegrally forming hook-shaped members on a sheet-form base from amoldable plastic is provided. The roll has a substantially circularcross section and hook-shaped cavities disposed about its periphery. Atleast many of the hook-shaped cavities each have a height of 0.020 in.or less and a tapered pedestal chamber and a crook chamber which areadjacent. Lower portions of the pedestal chamber are substantially widerthan the crook chamber such that space is provided for a formed hookmember to substantially recover the shape of the cavity while it isbeing pulled out of the cavity but before it is completely removed fromthe cavity.

Certain implementation of the foregoing aspects of this invention haveone or more of the following features. The apparatus, in certainimplementations, provides: the pedestal chamber tapers at a taper rateof at least 0.6 to 1 up to at least the half height of the hook shapedcavity; the taper rate is at least 0.8 to 1.0; the hook-shaped cavityhas a height less than about 0.015 in.; the hook-shaped cavity has aheight of less than about 0.010 in.; the cavity profile defines a hookhaving a crook portion, at least 40% of the width of the crook portionprojecting laterally from the pedestal chamber; the pedestal width thatcorresponds to the width of the crook portion corresponds with apedestal height of at least 30% of the total pedestal height above thebase; at least three contiguous face-to-face plates define cavitysections that together define one hook shaped cavity; the mold is a moldroll having a cylindrical shape; the cavity sections in the plates areformed by photochemical milling; the hook shaped cavity is set at anangle with respect to the plates; the hook shaped cavities areperpendicular to the plates; the mold is a mold roll and the hook-shapedcavities are arranged in a helical pattern about the mold roll; the moldis a mold roll and the hook-shaped cavities are aligned in across-machine direction; the hook shaped cavities have a displacementvolume of about 1.0×10⁻⁶ in.³ ; the hook shaped cavities have adisplacement volume of about 0.5×10⁻⁶.

A system for forming a hook fastener component may include certainimplementations of the foregoing aspects of the invention and, at amolding station, an extruder in the vicinity of the mold cavities fordelivering moldable resin. Certain implementations of a system includemeans for applying pressure to the moldable resin for promoting fillingof the mold cavities or that the hook shaped cavities are defined in theperiphery of a mold roll and further comprising a pressure rollerdisposed adjacent the mold roll for directing the resin into the hookshaped cavities.

According to another aspect of the invention, a mold for integrallyforming hook shaped members on a sheet-form base from a moldable resinis provided. The mold has hook shaped cavities located at the surface ofthe mold. At least many of the hook shaped cavities each having a heightof 0.020 in. or less and a tapered pedestal chamber and a crook chamberwhich are adjacent. The pedestal chamber has a base width greater thanabout the height of the hook shaped cavity. At half height of the hookshaped cavity, the pedestal chamber has a width equal to about half theheight of the hook shaped cavity, or more. The pedestal chamber has ataper rate of at least 0.6 to 1 up to at least the half height of thehook shaped cavity. The cavity profile defines a hook having a crookportion, at least 40% of the width of the crook portion projectinglaterally from the pedestal chamber. The pedestal width that correspondsto the width of the crook portion correspond with a pedestal height ofat least 30% of the total pedestal height about the base.

According to another aspect of the invention, a molded hook fastenerelement of a hook and loop touch fastener capable of engaging low-lyingloops of knitted material, or fibers of non-woven material and the likeof a mating fabric, is provided. The hook fastener element is formed bydelivering a moldable, heated material to a mold, the mold having amultiplicity of hook-shaped mold cavities arranged in an array. Eachhook-shaped cavity has a curved axis, a tapered pedestal chamber and atapered crook chamber. The pedestal chamber and the crook chamber arecontiguous and integrally formed. The pedestal chamber has a leadingedge and a trailing edge that slope inwardly toward each other atsimilar angles to the mold surface to define a truncated, broad-basedpyramid when viewed in side profile with a pedestal chamber base widthmeasured at the mold surface which base width is greater than about theheight of the mold cavity. The width of the pedestal chamber at the halfheight of the mold cavity is equal to about half the hook shaped cavityor more.

Certain implementations of this aspect of the invention have one or moreof the following features. The molded hook fastener, in certainimplementations, provides: the fastener is formed by extruding themoldable, heated material on the vicinity of the mold; the fastener isformed by pressing the extruded moldable, heated material into the moldcavities with a pressure roller disposed adjacent the mold; the mold isa molding roll and the moldable material is pressed into the hook-shapedcavities by a pressure roller disposed adjacent to the molding roll; themold is a solid mold and the moldable material is injected directly intothe hook-shaped cavities; the pedestal chamber tapers at a taper rate ofat least 0.6 to 1 up to at least the half height of the hook shapedcavity; the taper rate is at least 0.8 to 1.0; the hook-shaped cavityhas a height less than about 0.015 in.; the hook-shaped cavity has aheight of less than about 0.010 in.; the cavity profile defines a hookhaving a crook portion, at least 40% of the width of the crook portionprojecting laterally from the pedestal chamber; the pedestal width thatcorresponds to the width of the crook portion corresponds with apedestal height of at least 30% of the total pedestal height above thebase.

According to another aspect of the invention, a method of making asurface element from a moldable resin is provided. The moldable resin isdelivered to the surface of a mold such that the resin is forced intocavities located at the surface of the mold. The mold comprises a seriesof plates that are aligned and maintained face-to-face. Cut-outs in atleast adjacent three plates are aligned to define a mold cavity. Theresin is set in the mold cavities to form the surface element. Thesurface element is removed from the mold.

Certain implementations of this aspect of the invention have one or moreof the following features. The method, in certain implementations,provides: the surface element is a fastening element; the cavities havea hook shape; the hook-shaped cavities comprise a pedestal portion and acrook portion which are contiguous, the pedestal portion having apyramid shape such that, when viewed in side profile, the pedestaltapers at a rate of at least 0.6 to 1 up to at least half the height ofthe cavity and, when viewed in end profile, the pedestal tapers at arate of at least 0.6 to 1 up to at least half the height of the cavity;the mold is a molding roll and the cavities are arrayed on the peripheryof the molding roll, and the moldable resin is extruded onto the moldingroll in a machine direction and pressed into the cavities by a pressureroll, wherein the cavity has a component in the cross machine direction;the plates are formed by photochemical milling; the surface element is afastening element and the cavities have a hook shape, in which thecavity has a pedestal chamber which has a base width greater than aboutthe height of the hook-shaped cavity and, at half height of thehook-shaped cavity, has a width equal to about half the height of thehook-shaped cavity or more; the surface element is a fastening elementand the cavities have a hook shape in which the cavity profile defines ahook having a crook portion and a pedestal chamber, at least 40% of thewidth of the crook portion projecting laterally from the pedestalchamber; the pedestal width that corresponds to the width of the crookportion corresponds with a pedestal height of at least 30% of the totalpedestal height above the base.

According to another aspect of the invention, a method of making asurface element from a moldable resin is provided. The moldable resin isdelivered to the surface of a mold such that the resin is forced intocavities located at the surface of the mold. The mold comprises a seriesof plates that are aligned in a first direction. At least one cavity isdefined by cut-outs in at least three adjacent plates, which cavity hasa component which is perpendicular to the first direction. The resin isset in the mold cavities to form the surface element. The surfaceelement is removed from the mold.

Certain implementations of this aspect of the invention have one or moreof the following features. The method, in certain implementations,provides: the resin is injected into the cavities; the resin is pressedinto the cavities by a pressure roller disposed adjacent to the mold.

According to another aspect of the invention, a method of manufacturingplates used to form fastener elements comprising multiple hooks membershaving a height less than 0.02 in. integrally formed with a sheet formbase is provided. Cut-outs having predetermined shapes are disposed inthe plates. The plates are assembled in a predetermined relationship todefine a mold. A photoresist material is applied to at least one side ofa plate. The photoresist material is exposed to light in a predeterminedpattern. wherein the pattern is based on the desired form of said hookmembers and the pattern deviates from the profile of said desired formto compensate for the shaping properties of a chemical etchant. Aportion of the photoresist material is removed. The portion isdetermined based, at least in part, on the exposure to light. An acid isapplied to the plate for a predetermined period of time therebydissolving the portions of the plate exposed to the acid and creating acut-out.

Certain implementations of this aspect of the invention have one or moreof the following features. The method, in certain implementations,provides: the photoresist material is a positive photoresist materialand the exposure to light cures the photoresist material onto the plate,such that the photoresist material not exposed to the light is removed;the photoresist material is a negative photoresist material and theexposure to light burns the photoresist material, such that thephotoresist material exposed to the light is removed; the pattern oflight is determined by positioning a mask between a light source and thephotoresist material; the mask is applied to the photoresist material;the cut-out has a hook shape including a tapered pedestal chamber and acrook chamber which are contiguous, the lower portion of the pedestalchamber being substantially wider then the crook chamber; the plate isabout 0.006 in. thick or thinner; the cut-outs have concave sides;making a mask to achieve a desired cut-out shape including undersizingthe mask to achieve concave surfaces and oversizing the mask to achieveconvex surfaces; the plate is 0.006 in. or thinner, further comprisinglaminating a plurality of plates together to make a master plate; themold is a molding roll and the cavities are hook shaped and a componentof the hook shape extends in a cross machine direction; applyingphotoresist material to a second side of the plate; applying acid to theopposite sides of the plate for different time periods; the mask issized to achieve the predetermined shape of the cut-outs; the mask isoversized with respect to the cut-outs; the mask is undersized withrespect to the cut-outs.

According to another aspect of the invention, a method of molding amoldable material into a fastener element using plates manufactured inaccord with one of the foregoing aspects of the invention is provided.Certain implementations of this aspect of the invention have one or moreof the following features: a cavity is defined by cut-outs in at leastthree adjacent plates and the hook member ib formed by forcing moldableresin into the cavity, cooling the resin, and then removing the cooledresin from the cavity.

According to another aspect of the invention, a molded hook member for atouch fastener is provided. The hook member is integrally formed with asheet-form base in a mold having no moving parts. The molded hook memberis capable of engaging low-lying loops of knitted material, or fibers ofnon-woven material and the like of a mating fabric. A broad-based,tapered pedestal integrally formed with and extending upwardly from thebase, and a tapered crook portion integrally formed with and archingalong a curved axis directly from the top of the pedestal to a tip thatengages said mating fabric. In side profile, the pedestal has upwardlyextending leading and trailing edges that slope inwardly toward eachother at similar angles to the vertical to define a truncated,broad-based pyramid with a pedestal base width measured at the base.Projections of the leading and trailing edges intersect in the vicinityof the top of the hook, and at least 40% of the crook portion projectslaterally from the pedestal.

Certain implementations of this aspect of the invention have one or moreof the following features. The molded hook member, in certainimplementations, provides: projections of the leading edge and thetrailing edge intersect at an angle greater than about 40 degrees; theprojections of the leading edge and the trailing edge intersect at anangle greater than about 50 degrees; the taper of the pedestal is atleast four times as large as the taper of the crook portion; the hookmember has a height less than about 0.020 in., a thickness of about0.006 in. or less and is disposed on the sheet-form base at a density ofat least 1200 molded hook members per square in.

According to another aspect of the invention, a molded hook member for afastener is provided. The hook member has a tip portion capable of beingformed in a cavity of a mold having no moving mold parts, and capable ofengaging low-lying loops of knitted material, fibers of non-wovenmaterial, and the like of a mating fabric. A tapered pedestal isintegrally formed with and extending upwardly from the base. A taperedcrook portion is integrally formed with and arches along a curved axis.The tapered crook portion extends in a crook direction directly from thetop of the pedestal to a tip that engages the mating fabric. The profileof the molded hook member has a height less than about 0.020 in. fromits base and a pedestal base width of less than about 0.020 in., notcounting the fillets. The body of the hook member tapers continuouslyfrom the base to its distal tip. The taper of the pedestal is at least50 degrees. The hook member is thereby shaped so that the cavity inwhich the hook member is formed provides a space for substantiallyimmediate release for the tip portion of the hook member as it iswithdrawn from the mold to enable the crook portion to returnsubstantially to its molded shape after it commences dislodging from themold but before it is completely removed from the mold.

Certain implementations of the foregoing aspects of the invention haveone or more of the following features. The molded hook member, incertain implementations, provides: the displacement volume of the crookportion is less than 0.5×10⁻⁶ in. cubed; the tip is curved downgenerally in the direction of the base; the pedestal is 0.006 in. thickor less, and in which the hook members have a lineal density of 20 ormore members per in. in the crook direction; the hook members have alineal density of 60 or more members per in. perpendicular to the crookdirection.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 1a are side views of a mold cavity;

FIGS. 2 and 3 are side and top views, respectively, of a hook component.

FIGS. 2a, 2b, 2c and 2d are side, end, top and perspective views,respectively, of a hook member.

FIG. 4 is a schematic view of a system of forming hook members using amold roll.

FIG. 4a is a perspective view of a mold roll, in isolation. FIG. 4b is aclose-up, section view of the surface of the mold roll. FIG. 4c is aperspective view of an injection mold showing the orientation of a moldcavity diagrammatically.

FIGS. 5a and 5b are a series of side views showing a hook member beingremoved from a mold cavity in a mold roll, against and in the machinedirection, respectively.

FIG. 6 is a cut-away view of a mold cavity formed by several adjacentplates.

FIGS. 7a-7k are side views of sections of the plates in FIG. 6, showndiagrammatically.

FIGS. 8a and 8b are side views of sections of the plates in FIG. 6,shown diagrammatically, in which the cutouts have curved sides and awedge is formed at the top of the cavity.

FIGS. 9a and 9b are side and end views, respectively, of a hook memberhaving a wedge at the top.

FIG. 10a is a side view of a hook member having a curved side. FIGS. 10band 10c are cross-sectional views of the hook member shown in FIG. 10a.

FIGS. 11a and 11b are diagrammatic, perspective views of the surface ofa section of a mold roll depicting mold cavities having variousorientations with respect to machine direction.

FIG. 12 is an end view of a hook member having a taper running 90° tothe profile direction.

FIG. 13 is a prospective view of a hook member having a circularcross-section. FIGS. 13a and 13b are cross-sectional views of the hookmember shown in FIG. 13.

FIG. 14 is a plan view of a mold cavity used to form the hook member ofFIG. 13.

FIGS. 15 and 16 are diagrammatic views of a mold cavity, and a mask usedto form the mold cavity by photochemical milling. FIG. 15a is across-sectional view of a cavity formed by photochemical milling.

FIG. 17a is a side view of a microhook. FIG. 17b is a side view of asub-microhook. FIG. 17c is a side view of a sub-microhook in which thecrook extends essentially horizontally.

IMPLEMENTATIONS

Referring to FIGS. 1 and 1a, the profile of the mold cavity 1 of apreferred implementation of the invention is shown. It defines apedestal portion or chamber P and a crook portion or chamber C. Thepedestal portion has the profile of a broad based triangle, with itsrelatively straight sides projected to intersect at apex α in thevicinity of the top of the mold cavity. The mold cavity has a totalheight H and a half height of H/2.

The mold cavity profile of this preferred implementation has a basewidth B_(w), measured between intersection of projections 117 and 118 ofthe sides of the mold cavity with the base surface 110 of the mold, thatis greater than about the height H of the hook element; as shown, B_(w)is about 110% of the height.

At half height (H/2) of the mold cavity, the pedestal portion has awidth W_(p) about equal to the half height of the hook.

With an apex angle α of about 60°, the pedestal portion continuouslytapers from the base (ignoring front and back fillets 121 and 122) at ataper rate of about 1.2 to a point above the half height. The insidesurface 217 of the mold cavity then begins to curve to define the lowersurface of the crook portion, while the back surface 218 of the moldcavity profile proceeds straight for a further distance. The pedestalportion is considered to end where a tangent T to the inside surface 217is vertical. Referring to FIG. 1a, the pedestal height H_(p) is greaterthan the half height of the hook member.

The crook portion of the mold cavity tapers continually to its tip,though at a much lesser rate than the general taper of the pedestal. Inthe profile of FIG. 1a, the crook portion continues until its tipportion, directed downwardly, reaches the level of the top of thepedestal portion.

A hook component 100 of a touch fastener in accordance with a preferredimplementation of the invention is shown in FIGS. 2, 2a, 2b, 2c, 2d and3. The hook component consists of a sheet form base 10 and multipleparallel rows of integrally molded hook members 12 extending from thebase sheet. Ripstop bumps (not shown), i.e. known raised local regionsof the base in the spaces between rows of hooks, may be employed eitheraligned with the hook members or offset from the hook members, dependingupon the intended application.

Corresponding terms will be used to describe features of a hook memberproduced from the mold cavity. A broad-based, tapered pedestal 13 of thehook member is integrally formed with and extends upwardly from the base10. Preferably, the pedestal has a straight sided pyramidal shape whenviewed in side profile (see FIG. 2a). A tapered crook portion 14 isintegrally formed with the pedestal. The crook portion arches along acurved axis 15 directly from the top of the pedestal to a tip 16. Thetip is adapted to engage a mating fabric.

The width of the crook portion measured perpendicular to its curved axis(e.g., dimension D of FIG. 2a) continuously decreases from the pedestalto the tip.

In this preferred embodiment, the leading and trailing surfaces 17, 18of the pedestal form angles θ₁ and θ₂ relative to the sheet-form base,respectively, that are substantially greater than ninety degrees.Preferably, θ₁ and θ₂ are between about 110 and 130 degrees. Morepreferably, θ₁ and θ₂ are about 116 degrees and 125 degrees,respectively. Preferably, when the leading edge and the trailing edge ofthe hook profile are projected, they intersect at an angle α of at leastabout 40°, more preferably about 50°, and most preferably about 60° ormore. The axis 15 intersects the base at an angle φ that is preferablygreater than 80° and more preferably approximating 90°. Forming thepedestal as a truncated, broad-based pyramid when viewed in side profilesuch that the edges slant inward toward each other allows the hookmembers to be removed more easily from the mold cavity 1 because thecrook portion 14 can pass more easily through the portion of the moldcavity in which the pedestal was formed i.e., through the pedestalchamber. Furthermore, due to the relatively wide pedestal base width,each hook member is able to withstand relatively high shear loadsdespite the relative thinness of the hook member, which enables highercross-row densities of the hook members to be achieved. Furthermore, therelatively wide pedestal allows the hook member to better resistbending, thereby maintaining a better grip on the loops.

For use in important applications for the new hook component inconjunction with non-woven loop members (which may be only 0.001 in. indiameter and 0.0005 to 0.0020 in. high), the hook members are generallyquite small. Height 130 of the hook members 12 is preferably less thanabout 0.020 in., with 0.0150 in. or less being preferred for microhooks.Furthermore, the pedestal base width 19 for hooks of about 0.015 in.height--i.e., the width of the pedestal, taken parallel to the base 10at the level where the pedestal joins the base, disregarding the fillets21 and 22--is preferably between about 0.010 in. and about 0.025 in.,with about 0.0170 in. presently being most preferred.

Referring to FIG. 2d, the hook member has a displacement volume definedby a parallelepiped 110 having a bottom plane 101, first and second sideplanes 102, first and second end planes 103,104 and a top plane 106. Thebottom plane is oriented parallel to the base and tangent to the tip.The top is parallel to the base and tangent to the top of the hookmember at the point where the hook member achieves its maximum distancefrom the base. The side planes lie in the planes of the sides of thehook. The first end plane 104 is perpendicular to the bottom plane atthe point where the bottom plane intersects the hook member at itstrailing edge 18. The second end plane 103 is perpendicular to thebottom plane and tangent to the outermost portion of the crook. The moldcavity has a crook height H_(c), a crook width W_(c) and a thickness t.The displacement volume DV of the crook portion of the hook memberformed in the mold cavity is DV=W_(c) ×H_(c) ×t. The hook member has adisplacement volume of less than 1.0×10⁻⁶ in.³ and preferably about0.5×10⁻⁶ in.³ or less.

Referring to FIG. 1a, the crook projection, i.e. the distance the crookportion projects laterally from the top of the pedestal is shown as W₁,which is greater than 40% of the crook width W_(c).

This profile is also within the preferred rule that the height P₁ of thepedestal, at which the pedestal width W_(p) is equal to the width W_(c)of the crook portion, is at a height greater than 30% of the heightH_(p) of the pedestal.

Numerous advantageous implementations of the profile can be employed torealize microhooks of height less than 0.020 in. and displacement volumeless than 0.5×10⁻⁶ in³. In one specific implementation a hook memberhaving an overall height H of 0.015 in. is provided. The width W_(c) ofcrook portion is 0.013 in., the height H_(c) is 0.005 in., the thicknessis 0.006 in. and the displacement volume is 0.4×10⁻⁶ in³.

The fastener element 100 or hook strip, including the hook members, isadvantageously formed using the Fischer process, U.S. Pat. No.4,794,028, fully incorporated herein by reference, in which the moldcavities for rows of hook members are formed in the peripheries ofcorresponding disk-form mold plates, the plates being stackedalternately with spacer plates that form the flat sides of the hookmembers, with strengthening formations of bumps formed in the spacerplates that can add strength to the hook strip. In a preferredimplementation as shown in FIG. 3, in the machine direction (i.e. thedirection in which the strip being formed travels), there are preferablyabout 24 hook members per lineal inch. The hook members preferably arespaced apart laterally (i.e. in the cross machine direction) a distance23 of about 0.008 in., and the pedestals 13 preferably have a thickness24 of about 0.006 lineal in. This yields a density in the cross machinedirection of approximately 71 fastener elements per in. Hence, there arepreferably on the order of 1700 hook members per square in. in thispreferred embodiment.

As shown in FIG. 4, a preferred method for making such molded hookmembers entails extruding molten resin into the nip formed between acooled molding roll or roll mold 80 and a pressure-applying roll 82. Thecooled molding roll has mold cavities 1 about its periphery that areconfigured to produce hook members. A backing sheet 201, such as a wovenor non-woven fabric, may be supplied from a backing sheet roll 200 tothe nip. This backing sheet may contain loops adapted to engage the hookmembers. The resulting fastener element will then include hook membersbound to the backing sheet in what may be termed an in situ laminatingprocess.

Referring to FIGS. 4a and 4b, the molding roll comprises a series ofdisc-form plates or rings 250 mounted upon a cooled central barrel 251.The rings are pressed together axially to form a cylindrical surface.Spacer rings are disposed between the tool rings. The mold cavities aredisposed at the periphery of the tool rings between the spacer rings.The mold cavities and any bump or other formation cavities in the spacerring, are provided in a predetermined relationship to provide hookmembers on the base in a desired relationship, as the particularapplication requires. As shown, the molding roll is comprised of rings.However, circular plates having molds at their periphery and coolingchambers running through the plates can also be employed.

Because the hook members face in opposite directions, the hook membersin half the columns are oriented along the direction of travel of thefastener element, and the hook members in the other half of the columnsare oriented opposite to the direction of travel of the fastenerelement. As shown in FIG. 5a, a sequence showing the removal of a hookmember 12 from a mold cavity 1, the hook members that are orientedagainst the direction of travel can leave the mold cavities of themolding roll without significant bending. However, as shown in FIG. 5b,the hook members that are oriented along the direction of travel mustbend around the edges of the mold cavities as they are extracted fromthe cavities. This deforms them slightly, causing them to extend higherfrom the base sheet and at a slightly steeper angle than the hookmembers that are oriented against the direction of travel. Due to thevery small size of the hook members, there has been a tendency for theprior art hook members to cool and set in the deformed condition. Thehook-shaped cavity disclosed, however provides ample space for the crookto return to the shape of the cavity before the hook member iscompletely withdrawn from the cavity, thereby reducing the tendency ofthe hook to set in the deformed condition.

Furthermore, for making the two sets of hook members even more uniform,the hook members may be passed under a knock-down roller 86, the spacingof which, relative to wrap-around roller 87, is adjustable. Theknock-down roller may be employed to push any higher or steeper hookmembers back to the same level, relative to the sheet form base, as thelevel of the hook members that are oriented in the opposite direction.The knock-down roller 86 is located close to the position where the hookmembers are withdrawn from the cavities so that the hook members arestill slightly soft and permanently deformable when they pass under theknock-down roller and thus retain their new shape.

The mold cavities 1 are shown disposed at the periphery of the moldingroll 80 and the moldable resin is delivered to the surface of themolding roll at a nip. It will be appreciated that the moldable resincan be delivered to the mold cavities in numerous ways.

For example, the moldable resin can be delivered to the molding rolldirectly from an extruder. After traveling along the surface of themolding roll, the resin is then pressed into the mold cavities using apressure roller. In other cases, the extruder is mounted to extrude withpressure against the roll surface, with extensions of the nozzle surfacethat conform to the roll serving to keep the extruded resin atsufficient pressure to enable the mold cavities to fill with resin.

Other methods for delivering moldable resin to the mold cavities canalso be employed. For example, referring to FIG. 4c, which is aperspective view of an injection mold showing the orientation of a moldcavity schematically, the moldable resin is injected into the moldcavities 1 which are situated on an injection mold 150, thereby formingthe fastener elements by injection molding. The injection mold is formedof a series of plates 151 disposed face-to-face to create a flat (orcurved) surface having mold cavities. The mold cavities can be formed inone or more plates. After molding, the overall mold opens, the hooks arewithdrawn from the mold cavities as the molded piece is removed and theoverall molds closes for another injection cycle. Injection molding canbe employed to form the hook members directly on a rigid backing which,in turn, can be attached to a separate part. Injection molding can alsobe employed to form the hook members integrally with a part, such thatthe hook members do need to be later attached to the part.

The moldable resin may be any plastic material depending on the intendedapplication for the fastener element. Currently, polypropylene ispreferred. Nylon, polyesters, polyethylene, propylene, ethylene andcopolymers thereof, or other thermoplastic resins may also be readilyemployed.

Other important aspects of the invention concern the making of productsthat employ three or more mold plates that define the mold cavities.This technique is especially useful in forming hooks by the roll moldingprocess that have a cross machine orientation or in forming hooks thatextend cross-wise to the planes of assembled plates in a stationarymold. These plates are preferably formed by use of specializedphotochemical milling techniques. Alternatively, EDM techniques, lasermilling or other techniques can also be employed to form the plates.

For example, FIG. 6 is a cut-away view of a molding roll through aradial plane 6--6 of FIG. 4a. Photochemical milling technology or otherhigh accuracy forming techniques, such as laser milling, are employed toform mold cavities that extend in the cross machine direction of themolding roll. As shown, the mold cavity is hook-shaped. However, othershapes can be employed, if it is desired to form other fastenerproducts, or even to form elements that perform other functions.

In FIG. 6, the mold cavity is formed by a plurality of stacked disk-formplates which are assembled face-to-face on the roll axis, therebydefining the surface 110 of the molding roll. Each successive plate hasmaterial removed a different amount according to slices taken of theprofile of the desired mold cavity, so that only a portion of the cavityis formed in each plate. Typically part of the cavity is formed by athrough aperture in one plate, while plates on each side of that platehave cavity portions in at least part of the thickness of the plate.

As shown in FIG. 6, the plates all have the same thickness. According tothe invention, however, in certain advantageous implementations, theplates have differing thicknesses, based on the intended application ofthe hook, the desired profile or the density of the feature formed. Incertain applications, the use of plates of differing thickness enablesmore economical fabrication since fewer plates are required to form themold cavity. Further, the use of plates of varying thickness in otherinstances enables efficient definition of the mold shape, or theachievement of curved surfaces of exceedingly small radius and/orsmoother transition. In important cases, as the radius curvature of afeature becomes smaller, thinner plates are employed to enable betterdefinition of the surface.

The plates may be only 0.003 or 0.004 in. thick or less when formingsmall hooks. According to the invention, to enable use of very thinplates for forming special features, prior to assembling to form themold (either a stationary mold or roll mold) one or more of the thin anddelicate plates are laminated together to create a more rugged masterplate that can be readily assembled on the cooled barrel without risk ofdistortion. The plates may be laminated by brazing, high temperature,long life bonding agents, etc.

Returning further to discuss FIG. 6, in plate h, for example, the cavitysection extends through the entire thickness of the plate in the areas308 and 309. In plate k, the cavity section extends through only aportion 314 of the thickness of the plate, to define the tip of the moldcavity.

In this approach, usually each plate is different from its neighbor andonly by the stacking of the plates together is the mold cavity formed.In this way, hook members in the cross plate direction may be produced(cross-machine direction in the case of roll molding).

One can produce by this technique hook members that have flat surfaces.Advantageously, however, hook members are produced that have roundedsurfaces in some or all regions, from base to tip. Advantageously,according to the invention, surfaces at the tops of the hook tips aremade to taper to a point to give a wedge-shaped effect to the top of thehook member that assists the entry of the top into the face of a matingfabric.

FIGS. 7a-7k show, in diagrammatic form, a series of cut-away sections ofrings that correspond with rings a-k of FIG. 6. The ring lettered a hasa small section 300 of the outer edge removed, representing a section ofthe backside of the hook 400. The next ring, b, has cavity section 301that forms the next section of the backside of the hook. The cavitiesthrough ring h become successively taller to form corresponding sectionsof the backside of the hook.

In ring h, cavity section 308 forms a section of the pedestal of thehook that is diminished in height, representing the transition towardthe other side of the hook. Cavity section 309 forms the beginning ofthe top of the crook.

In the next ring, i, the cavity section 310 is diminished to representthe pedestal becoming shorter while cavity section 311 forms the part ofthe crook that progresses downward. At ring j, cavity section 312 is thelast section of the pedestal and cavity section 313 approaches the tipof the crook. Finally, in ring k, cavity section 314 forms the actualtip of the hook. Since there is no portion of the pedestal formed byring k, there is only one cavity section in this plate.

The techniques described enable one to optimize the shape of theselected areas, especially in section h, i, j and k. FIGS. 8a and 8bthus shows an alternate way of creating a mold cavity that, according toa further aspect of the invention, is achieved by photochemical milling.The cavity sections 300-314 in FIG. 7, have straight sides which producea hook member with flat sides; by changing to curved sides as in FIGS.8a and 8b, as a result of the inherent tendency of photochemical millingto form curved surfaces, a hook member is created that has curved sidesrather than flat sides. As the crook is approached in plate H', thecavity section 309' not only has curved sides, but it has a point toproduce a crook of wedge form at its top.

FIGS. 9a and 9b show a hook in which the top of the crook is wedgeshaped, created by the cavity sections 309' such as illustrated in FIG.8b. The top of the hook member thus has a two-sided wedge effect toseparate the fibers or the filaments of the mating fabric and allow thehook member to penetrate the surface and subsequently engage better intothe loops or with the fibers.

FIGS. 10a, 10b and 10c show a hook member which is formed by milling thehook shape by photochemical milling techniques into one ring anddefining the cavity with the milled ring and a flat ring. The hookmember is curved on one side and flat on the other. Consequently, aone-sided wedge is formed at the top of the hook member to betterpenetrate loops.

The techniques just described, of creating curved surfaces to the hooksto form top wedges or smooth non-abrading surfaces, are applicable toformation of hooks that extend, as desired, in either the direction ofthe plate (machine direction for roll molds) or in the cross plate(cross-machine direction for roll molds).

An advantage of making hook members in the manner just described, inwhich the hook member is aligned in the cross machine direction of themolding roll concerns the manufacture items of apparel. A tape ofconventional hook form is often employed in an orientation that does notpoint the hooks in the optimum orientation. Molding hooks in a crossmachine direction, for such cases, enables the points of the hooks onthe tape to point in the direction to optimize the engagement into theloops or with the fibers.

The sectioned technique described with respect to FIGS. 6-8,advantageously enables hooks of different size and shape to be createdwhich vary along the length of the product to accommodate the conditionsof various parts of the use of the fastener. Advantageously, the hooksizes and shapes are likewise varied around the circumference of thetooling as suggested in FIG. 10. Likewise, in certain advantageouscircumstances, the sizes of the hooks are varied in the machinedirection. Thus one achieves hooks of different sizes extending in bothdirections, interspersed with each other, according to a predeterminedpattern. In certain implementations, adjacent hooks lie at 90 degrees toeach other in a repetitive pattern in both directions. Also, accordingto predetermined patterns, machine direction hooks are alternated withcross machine direction hooks to reduce the sensitivity of the productto orientation.

Using the techniques just described, the invention also enables hooks torun at an angle relative to the cross machine and machine direction,i.e. in a helical or biased configuration such that a component of theprojection of the hook member extends in the cross machine direction andin the machine direction. For instance, in certain embodiments, ringsare formed such that the hooks extend at an angle of 45 degrees to themachine direction if that is needed. FIGS. 11a and 11b which areperspective views of a section of the surface of a mold roll showing thelocation and orientation of mold cavities schematically illustrate thesevarious orientations. Like orientations (with-the-plate, andcross-the-plates orientations) are achieved for fixed molds, accordingto the invention.

The present techniques therefore enable practical manufacture of hooks(including hooks with multiple crooks) having various orientations(i.e., components of the hook extending in the cross machine direction)and patterns relative to the machine direction of the molding roll. Palmtree hooks (dual hooks), trident hooks (three hooks) and quadra hooks(four hooks fasteners) are made feasible according to the techniquesdescribed here.

The molding action of the hook shown in FIG. 6 will now be described. InFIG. 6, the same profile that has previously been described in FIG. 1 isshown, except that it has been rotated 90 degrees relative to themachine direction.

The pedestal base is wide, to allow the hook to demold and spring backto its original shape before it clears the pedestal cavity, to reducedistortion, as described above. A further feature of the design is thata wide pedestal also is provided in the machine direction. Thiseffectively produces a pedestal that is broad both in the crookdirection and at 90 degrees to the crook direction, effectively forminga true pyramid pedestal that tapers in on all four sides.

FIG. 12 is the end view of a hook member mold employing the sectioncavities of FIG. 8, but having tapers running 90 degrees to the profiledirection (i.e., in end view). In certain advantageous instances, thetaper rate is 0.6 to 1, 0.8 to 1 or more. In certain advantageousinstances, the taper in end view matches the taper in side profile,about 1.2. This provides a very substantial pedestal which enables thehook member to perform well because it is sturdy and well anchored. Ofcourse, other profiles are made possible by the invention.

The taper shown in FIG. 12 also enables the hooks to be readilydemolded. According to the invention, tapers of the pedestal areselectable that simultaneously enable demolding of cross machine hooks,provide a large pedestal cavity for the crook of the hook member to snapback to molded shape as demolding progresses, and provide hooks that arevery strong relative to their small overall height.

In addition to enabling production of a pedestal with tapers in bothmachine and cross machine direction, according to another aspect of theinvention, the techniques are employed to introduce curved surfaces andto create a molded pedestal that is of cone shape as shown in FIGS. 13,13a, 13b and 14. The conical shape provides a sturdy hook, but withsmooth surfaces that in important instances enable the avoidance ofabrasion that sharp corners or flat surfaces produce.

Round surfaces of the hook members also in certain circumstances reducefatigue fracture at sharp corners. Without sharp corners, such hooks mayreturn to their original shape during disengagement because they do notso readily suffer fatigue. Also such rounded hooks are capable of anincreased number of cycles of fastening and unfastening before failure.

Special photochemical milling techniques have novel use in forming thenumerous microhooks described above or submicrohooks to now be describedof conventional and cross orientation.

In the making of a mold for the hook profile shown in FIG. 6, accordingto this aspect of the invention, photochemical milling techniques areemployed. For a given plate, a piece of flat sheet stock is selectedfrom which the mold cavity or cavity section is to be formed. In thecase of a roll mold or molding roll, the sheet stock is sized to form acomponent disk of the molding roll. The material may be 17-7 Phstainless steel or other suitable metal. A photosensitive media, i.e. apositive photoresist material, is applied over the plate and is exposedto a light source through a compensating mask so that the photoresistwill be removed where it is desired, to enable photochemical milling toremove metal to form the mold cavity. The mask blocks a predeterminedportion of the light so that the photoresist material is exposed to apredetermined pattern of light. The mask positioned between the lightsource and the photoresist material. In particular, the mask may beapplied directly to the photoresist material.

Currently, the photoresist material is preferably a positive photoresistmaterial. When exposed to light, the positive photoresist material curesonto the plate. The remaining portion of the photoresist material whichwas not exposed to light is then removed. Alternatively, a negativephotoresist material may be employed. When exposed to light, thenegative photoresist material is "burned" away. The remaining portion ofthe photoresist material which was not exposed to light remains on theplate.

In FIG. 15, the mask is shown in dashed lines, superposed over theprofile of the desired hook shaped cavity, shown in solid lines. Theportion of the photoresist that is to be removed is within the dashedlines. After the photoresist is exposed to the light, the photoresist iswashed away to expose the pattern of the art work. Then the metal sheetis placed in a machine, and the metal not covered by the photoresistmaterial is removed by action of acid. Spray of acid is employed, as isconventional in photochemical milling. After milling, the portion of themetal plate covered by the photoresist layer remains. (As is known inthe field, positive or negative photoresist material may be employed toform the photoresist layer, positive resist being presently preferredwhere extremely small features are being produced.) With respect to FIG.15, regions A-G designate different portions of the shape of the cavityand, diagrammatically, of the compensating mask. In some regions, thedashed line of the compensating mask and the edge of the desired cavitygenerally correspond, while in other regions they do not. For straightline regions, e.g. region B in FIG. 15, the edge of the compensatingmask generally corresponds to the straight line of the cavity profilethat is desired (the shallower the mill depth, the closer thecorrespondence). However, in curved regions, the lines of the maskdiverge more substantially from the desired profile. The more radicalthe curvature is, the greater is the difference between the mask and thedesired profile. In areas where the curve of the desired cavity edge isconvex, such as at A in FIG. 15, the compensation is to opposite effectto the compensation where the curvature is concave, as at C in FIG. 15.In general, in convex regions of the final edge, as at A, thecompensating mask undersizes the cavity because the action of the acidwill be relatively concentrated for a given length of perimeter beingmilled, relative to what occurs for a straight line portion.

On concave surfaces, as at C, the opposite is true and the art work ofthe compensating mask is enlarged to compensate in the opposite way.Moving to region E in FIG. 15, in this case the convexity of the surfaceis greater than in region A, i.e. has a smaller radius, and thereforethe compensation is greater, providing more undersizing of the cavitydefined by the mask.

The art work of the compensating mask defines points in the regions Dand E. The tendency in photochemical milling is for sharp corners to berounded. In this case, since a small rounded tip shape is desired, thecompensated art work comes to quite a sharp point. Region F is astraight line, similar to region B, and region G corresponds to regionA. Thus the hook cavity profile for all regions of curvature in the artwork of the compensating mask in this example is different from theactual design of the desired hook cavity.

FIG. 15a shows a cross section of the metal after action of the acid inwhich advantage is taken of the tendency in the photomilling process toproduce a curved rather than a straight surface due to the nature of theaction of the acid. The general principle is that at sharp edges, theprocess will produce a rounding of the edge surface. This is found togenerate a desirable rounded shape, particularly at the edge of the topof the hook. The rounded shape provides a surface that can more readilypenetrate the surface of a mating fabric than a flat surface. Further,in important instances, the naturally rounded shape of the surface ofthe milled plate is exploited to create a smooth curve extending alongseveral adjacent plates.

Selection of the particular compensating techniques for the art work,the photoresist materials, and the acid depend upon the particular metalbeing exposed, the depth of metal removal and other conditions, as iswell known in the art of photochemical machining. For general reference,see for instance: technical paper 1976 Society of ManufacturingEngineers, entitled "Photo-Chemical Machining Fundamentals--With ThreeUnique Applications" by Dr. R. J. Bennett; and publication PhotoChemical Machine Institute, publication no. PCMI1000, entitled "What isPhoto Chemical Machining Process and What Can It Do For You?"; toconference proceedings of The Society of Carbide and Tool Engineerscosponsored by Medicut Research Associates, Inc and Abrasive EngineeringSociety, entitled "Nontraditional Machining Conference Proceedings ofthe Conference Held Dec. 2 and 3, 1985"; and to the references cited inthose papers.

FIG. 16 illustrates an alternative compensating mask in which thestraight lines and sharp corners are used to provide smooth, smallradius surfaces in the produced part. The art work is shaped as smallsquares near the tip of the hook where a smooth radius of one curvaturetransitions into a smooth radius of the opposite curvature.

Various techniques are employed to obtain different desired profiles onthe plates. For example, in producing cavities or cavity sections thatextend through the plates, the plates are advantageously photochemicallymilled from both sides, thereby reducing the total concavity of themilled surface, and, in certain circumstances where desired, providingoverall convex surface. In certain advantageous instances, the sides ofthe plate are exposed to the acid conditions for different amounts oftime, that create different shapes at the opposite sides of the plate.The acid liquid is preferably directed in a stream at portions of theplate, that increase its effectiveness.

Referring to FIG. 17b, a hook element according to FIGS. 2a-d isprovided having an overall height H of 0.008 in. The radius of the tipsurface is approximately 0.0008 in. This hook is shown for comparisonnext to a microhook in FIG. 17a, having height H of 0.015 in., describedearlier. Because it is diminutive (height less than 0.010 in.) we referto the hook of FIG. 17b as a "sub-microhook". It has been advantageouslyformed in different instances by photochemical milling into the side ofa plate to a depth of 0.003 in. and 0.005 in, The hook element of FIG.17c is of similar configuration except that the projection of the crookis not as great and the top of the crook extends essentiallyhorizontally. This profile represents a different trade off in respectof displacement volume and hook shape that is appropriate in certaincircumstances. The displacement volume of the hook member of FIG. 17c isless than that of FIG. 17b because it omits the downward projection ofthe tip. This form of hook is considered to be useful e.g. with nonwovenfabrics in which the fibers are tightly bound to the material andpresent little loft. When employed in close association with rows ofhook elements pointing in the opposite direction, the hooks of FIG. 17cprovide effective engagement in certain instances.

Other embodiments are within the scope of the following claims.

What is claimed is:
 1. A method of manufacturing plates that areassembleable in a stack to provide a mold to form a fastener productthat has an array of closely-spaced hook members of desired form, thehook members being of a height less than 0.02 inch and integrally formedwith a sheet form base, the plates having predetermined portions removedto form cavities of desired form in the plate, the plates being adaptedto be assembled in a predetermined relationship so that the cavitiesdefine molding cavities for the array of hook members, the methodcomprisingapplying a photoresist material to at least one side of achemical-etchable plate; exposing the photoresist material to light in apredetermined pattern wherein the pattern is based on said desired formof said hook members and the pattern deviates from the profile of saiddesired form to compensate for the shaping properties of a subsequentchemical etchant application; removing a portion of the photoresistmaterial which portion is determined based, at least in part, on theexposure to light through said predetermined pattern; and applying achemical etchant to the plate thereby dissolving the portions of theplate exposed to the chemical and creating said cavities.
 2. The methodof claim 1 wherein the photoresist material is a positive photoresistmaterial and the exposure to light cures the photoresist material ontothe plate, such that the photoresist material not exposed to the lightis removed.
 3. The method of claim 1 wherein the photoresist material isa negative photoresist material and the exposure to light burns thephotoresist material, such that the photoresist material exposed to thelight is removed.
 4. The method of claim 1 wherein the pattern of lightis determined by positioning a mask between a light source and thephotoresist material.
 5. The method of claim 4 wherein the mask isapplied to the photoresist material.
 6. The method of claim 4 wherein atleast some of the cavities each have a hook shape including a taperedpedestal chamber and a crook chamber which are contiguous, the lowerportion of the pedestal chamber being substantially wider then the crookchamber.
 7. The method of claim 4 wherein the plate has a thickness, thethickness being about 0.006 inch.
 8. The method of claim 4 wherein thecavities are defined by concave sides of the plates.
 9. The method ofclaim 4 further comprising shaping the mask to achieve a desired cavityshape, by undersizing the mask in the region of desired concave surfacesand oversizing the mask in the region of desired convex surfaces. 10.The method of claim 9 comprising applying acid to the opposite sides ofthe plate for different time periods.
 11. The method of claim 9 whereinthe mask defines relatively sharp points for forming hook members withrelatively rounded tips.
 12. The method of claim 4 wherein the plate hasa thickness, the thickness being about 0.006 inch or less, furthercomprising laminating a plurality of plates together to make a masterplate.
 13. The method of claim 4 wherein the mold is a molding roll andthe molding cavities are hook shaped and a component of the hook shapeextends in a cross machine direction.
 14. The method of claim 4 whereinthe mask is sized to achieve the predetermined shape of the cavities.15. The method of claim 14 wherein the mask is oversized with respect tothe cavities.
 16. The method of claim 14 wherein the mask is undersizedwith respect to the cavities.
 17. A method of molding a moldablematerial into a fastener element using plates manufactured in accordwith claims 4 or 12 wherein at least some of the molding cavities areeach defined by cavity portions in at least three adjacent plates andthe hook members are formed by forcing moldable resin into the moldingcavities so defined, cooling the resin, and then removing the cooledresin from the molding cavities.
 18. The method of claim 1 furthercomprising applying photoresist material to a second side of the plate.19. The method of claim 1 wherein the pattern defines cavities adaptedto form hook members having a height of less than about 0.010 inch. 20.The method of claim 1 wherein the plate is etched to create cavitieshaving a depth of between about 0.003 and 0.005 inch.
 21. The method ofclaim 1 wherein the created cavities are adapted to form hook membershaving wedge-shaped crook tops.
 22. A method of forming cavities in theside of a mold plate adapted to be assembled with other plates in apredetermined relationship to define a mold for integrally molding anarray of fastener hook members of a height less than about 0.020 inchextending from a sheet form base, the cavities defining hook membermolding cavities when the plates are assembled; the methodcomprisingapplying a photoresist material to a side of the mold plate;providing a compensated mask defining a shaped, pointed mask aperturecorresponding to each cavity; exposing a predetermined portion of thephotoresist material to light through the mask apertures of thecompensated mask; removing a portion of the photoresist material toexpose regions of the plate corresponding to the desired cavities, whichportion is determined based on the exposure to light; and applying achemical etchant to the plate to dissolve plate material at the exposedregions to form said cavities.
 23. The method of claim 1, or 22 whereinthe chemical etchant is applied to the plate in a manner to etchentirely through the thickness of the plate so that at least some of thecavities extend through the plates.
 24. The method of claim 23 whereinthe etchant is applied to both sides of a plate in a manner cooperatingto etch entirely through the thickness of the plate.